Earplugs are currently rated with an EPA governed Noise Reduction Rating (NRR). The Noise Reduction Rating (NRR) is the measurement, in decibels, of how well a hearing protector reduces noise as specified by human subject testing as regulated by the Environmental Protection Agency. The higher the NRR number the greater the noise reduction.
Earplug fit affects the effective noise reduction ratio of an earplug. For example one study illustrated that a good fit of the earplug has an NRR of 33 dB, while the same earplug fitted poorly provided an NRR of 0 dB.
In the industrial noise environment the use of hearing protection is paramount. The correct fit of the hearing protection often determines its usefulness. Thus the fit of an earplug is important. Current earplugs have various levels of ease of fit. Professional training can increase the effectiveness of earplug fit, however many users do not have access to professional training. Thus a system that improves the chance of improved fitting will be beneficial to protecting hearing in many users.
Several systems have been developed in the past. For example: Wasserman (U.S. Pat. No. 2,876,767) illustrates (FIG. 7, U.S. Pat. No. 2,876,767) a system requiring an external pump to inflate an inflatable bladder as does Pierre (FIG. 5, U.S. Pat. No. 4,896,679); Rose (U.S. Pat. No. 4,089,332, FIGS. 1-2) illustrates an earplug 10 with a first end 14, that when deformed into a second stable position results in the extension of a second end, the system lacking a method for maintaining a pressurizing force, thus lending itself to possible de-inflation; Krause (U.S. Pat. No. 5,483,027) illustrates a bi-directionally inserted earplug with a two-way valve to maintain a chamber in an expanded condition, while Michael et al. (U.S. Pat. No. 2,824,558) illustrates an earplug with a one-way valve.
Unlike related art, a simplified system (for ease of adoption) designed for use in a particular and adjustable pressure range to provide the necessary sound isolation would be useful.